Heretofore, a plug and a socket which are attached to a liquid storing container for storing a drug solution or the like used for semiconductor production have been known (for example, see Japanese Unexamined Patent Application, Publication No. 2009-173326 (hereinafter referred to as “JP 2009-173326”)).
In the plug and the socket disclosed in JP 2009-173326, the inside of a container is pressurized with a gas supplied from a gas supply pipe to the socket and a liquid contained in the container is guided to an external line via a siphon tube, the plug, and the socket.